Warpage in HDPE moulding?

Daniel, there are ways however you have not provided enough information on the part.

06-25-2014 11:20 上午

Top #4

Jeson Chen

Hi Daniel

I have some suggestions for you. Please consider this trouble from below ways
1) Is the part suitable for design to deformation factor ?
2) The injection molding parameters. if this is very easy to deformate regularly, you can make a reverse deformation in tooling fabrication.
3) you can use a fixture to keep the part correctly after molding .

4) Change the material to stable dimension material, such as engineering plastic .

Hope it can help you .

Thanks

Jeson

06-25-2014 02:13 下午

Top #5

Henry Mora

When injection molders ask these questions, that means that the mold is already built, the steels called out, ejection locked in, the cooling set and the part has been designed and probably on the market. HDPE inherently is not dimensionally stable enough to hold tight tolerances. Jeson's #2 suggestion is pretty much what you're left with. As Edgar said, you haven't supplied enough info to proceed. I believe that HDPE is delegated to limited applications such as toys or maybe caps.

06-25-2014 04:18 下午

Top #6

Scott Gray

I will agree with Henry a reverse deformation in the mold steel will allow for you to use the most efficient molding parameters and cycle times.

06-25-2014 06:46 下午

Top #7

Daniel Cohen

Hello all,
you are right, of course. the mold is built and the part on the market.
we are talking about a panel, 1.3X0.9 m
6 valve gates 5.5mm diameter
pretty symetrical but with a lot of ribs criss crossing it, left-right, top-bottom, and diagonally (and symetrically both ways).
what we see is the middle section rising above the plane of the perimiter around the center nozzles.
also, 10% talc did not help.
Daniel

06-25-2014 09:35 下午

Top #8

Tom Peeler

Hi Daniel,
I would be happy to discuss this with you. I think it may need more than a few email exchanges.
Tom

06-25-2014 10:05 下午

Top #9

jacky sun

it is difficult to say how to, and I don't agree at the advice for reverse deformation . be careful, don't do that.

1. lower down the mold temp. and barrel temp.
2. lower packing pressure a little. but don't keep it too low.
3.prolong the cooling time.
4.checking the cooling line.
5.change the injection speed, not too faster .
6.using high pressure with low speed.
7.check the nozzle temp. which should lower a litter than barrel temp. maybe 5 celsius degree. and cooling enough close around each nozzle.

maybe more, we should had stayed on the site.

yeap, talc doesn't work.

06-25-2014 10:23 下午

Top #10

Roger Xie

Hi, Daniel,
I think you should consider internal stress issue on your product. At first, you can do a mold flow to confirm if the gate location and size is suitable for the structure. If not, adjust gate. Second, you can trial mold to shot different time by several times and see if material flow as you imagine. If not, adjust gate or vent. All above work is just to decrease internal stress of molding. Hope it is helpful.